Setting up the FRITZ!Box for use with another router

The FRITZ!Box can share the Internet connection of another router. You can then do the following with the FRITZ!Box:

use it with an Internet connection where the Internet service provider requires the use of a special router they provide that contains preconfigured account information that cannot be changed (Integrated Access Device, IAD).

easily integrate it into an existing network infrastructure.

use it as a PBX and then use all of the telephones connected to the FRITZ!Box to conduct calls over the router.

The FRITZ!Box can be set up as an IP client or a cascaded router. Which operating mode is best depends on your requirements.